Resistors are used in electronic circuits for various reasons such as for limiting current flow, or for producing a voltage drop in a voltage supply line. Resistors may also be used in signal monitoring systems for observing signals present in an electronic circuit. When used as part of a signal monitoring system, a resistor is typically configured not to interfere or to modify a signal being monitored. For example, a low value resistor may be connected to a part of an electronic circuit to monitor the current signal flowing through the resistor and an observation instrument such as an oscilloscope coupled to the resistor. The voltage generated across the resistor can be observed on the oscilloscope in order to obtain information about the current signal. Such an arrangement works quite effectively when the signal is a DC signal or a time-varying signal having a frequency that is relatively low. However, when the circuit is a radio-frequency (RF) circuit, the inherent inductance presented by the various parts of a resistor, particularly a leaded resistor, may introduce distortion or disturbance into an RF signal propagating through the RF circuit.
The shortcomings associated with using a leaded resistor in high frequency circuits may be alleviated to some extent by using resistors that do not have leads (surface mount resistors, for example). However other factors such as the inductance contribution of metal tracks used for interconnecting the surface mount resistors; wires used for connecting the surface mount resistors with other circuit components; leads present in other components such as RF connectors; and component layout close to surface mount resistors, can have an adverse impact upon RF signals, particularly RF signals at higher frequencies.
It is therefore generally desirable to minimize the inductance contribution of various components, such as resistors and current propagation paths, in a signal monitoring system that is used for observing RF signals in RF circuits.